Not Applicable
1. Field of the Invention
This invention relates to the field of probes. More specifically, the invention relates to an ultrasonic probe head for measuring volume flow in vessels, particularly blood flow in arteries and veins, and the use of such probe head during conventional and endoscopic surgery.
2. Description of Related Art
Ultrasound probes are used in several applications, one application being the measurement of volume flow in vessels in connection with surgery. Prior art probe heads for measuring volume flow in vessels (e.g. veins and arteries) are generally based on the fact that the time required for ultrasound to pass through the vessel fluid is slightly longer when the ultrasound is transmitted against the fluid flow, than when it is transmitted in the same direction as the flow. In order to generate such transmission and record the difference in transit time, prior art probe heads for measuring volume flow in vessels in general and in principle comprise two crystals for transmitting and receiving ultrasound waves, and a passive device for reflecting same. The crystals are disposed on the one side of the vessel, at equal but opposite angles with respect to a plane perpendicular to the vessel longitudinal axis. The reflecting device is disposed on the other side of the vessel, diametrically opposite the crystals. The crystals and the reflector are arranged such that ultrasound waves reciprocally travel from one crystal, through the vessel, being reflected off the reflector, and returning through the vessel to be received by the other crystal. In order to having the ultrasound waves travelling in an as homogenous medium as possible, the gaps between the vessel and the crystals and between the vessel and the reflector, are filled with an acoustic transmitting fluid, such as e.g. blood or water orxe2x80x94if the vessel is not otherwise immersedxe2x80x94an acoustic coupling gel.
In order to keep the vessel in a fixed and stationary position between the crystals and the reflector during measurement, prior art probe heads are equipped with a sliding device, which is opened to receive or release the vessel and closed to retain the vessel.
It is in e.g. surgical procedures, essential that the vessel remains in a stationary and fixed position within the probe head. It is also important that the gel is kept in place between the vessel and the probe head in order to ensure reliable measurement.
One problem with known probe heads is that the gel is not well contained, and that flow measurements over extended periods of time thus are compromised due to the influence of air or other fluids having different acoustic properties.
Known probe heads are also cumbersome to operate, in that they require the actuation of movable sliding devices in order to place the exposed artery or vein in the probe head. This can at best be difficult to accomplish, given the environment in which the probe heads are being used, and the small size of the probe heads.
Conventional probe heads must also to some extent be disassembled for cleaning and sterilisation after use. This is time consuming and exposed the probe heads for excessive wear.
It is therefore a long felt need for a probe head intended for volume flow measurement in vessels, that is easy to manufacture, operate and clean, and that retains the gel for an extended period in order to maintain sufficient acoustic coupling.
The present invention solves that need, in that the probe head according to the invention contains few parts that are easily manufactured by conventional techniques and, when assembled, comprises one sealed unit with no movable parts. The invented probe head is thus easy to clean and sterilise, requiring no disassembly and reassembly. Furthermore, the vessel may easily be placed in the invented probe head, only by the user slightly twisting the probe head. The probe head in accordance with the invention also comprises a channel which in an improved manner retains the gel for an extended period, thereby ensuring sufficient acoustic coupling.
These and other objects and features of the invention are provided by an ultrasound probe head for measuring volume flow in vessels. In broad terms, the probe head comprises a housing, a support element, reflector-, crystal- and circuit means, and associated wires and cable.
The ultrasound reflector, piezo-electric crystals and circuit board are mounted onto respective dedicated surfaces in the support element, in an arrangement generally known in the art and electrically connected through wires to a measurement apparatus.
Inclined surfaces to which the crystals are mounted, are disposed in the upper region of the support element, symmetrically about a support element vertical axis. The support element is furthermore equipped with a bore for passing the electrical cable and a slit and a wire compartment for housing the electrical wires.
The ultrasound reflector is attached to the support element by fastening means, while the crystals and circuit board are affixed to the support element by means of a resilient compound. The support element, with the above mentioned parts assembled to it, is sealably coated with a resilient compound.
The probe head housing is made of a resilient material and comprises a compartment into which the support element is placed, a cable bore for the electrical cable bundle containing the wires to the crystals and circuit board, a recess into which a portion of the reflector is passed, spill guards for limiting acoustic coupling gel spillage, and vessel retainer flaps for retaining the vessel in a stationary position in the probe head while measurements are being performed.
The assembled probe head housing and support element are further sealed to constitute one sealed probe head unit, by the application of a resilient compound in the upper region of the housing.
The resilient compound filled in the upper region of the housing, above the affixed crystals and circuit board, forms together with the vessel retainer flaps, part of the reflector and the gel spill guards, a channel with generally planar surfaces, capable of receiving, supporting and retaining the vessel and an acoustic coupling gel.
The resilient vessel retainer flaps are flexible in order to letting the vessel be slipped into the channel. The flaps secure the vessel in a stationary position in said channel, and are sufficiently flexible for allowing a selective release of the vessel from the channel.
The assembled probe head may be used in connection with conventional surgery, where arteries and veins are exposed, and may be fitted to any known probe type. The assembled probe head may also be used in endoscopic procedures and may be fitted to any known endoscopic probe type.
The gel spill guards upper region or edge may have either an arcuate (concave or convex) horizontal or inclined shape.
The probe head housing upper lateral edges are formed as inwardly directed flanges adapted to catch the support element upper region.